Pat the steaks dry with paper towels. Season with 2 teaspoons of the salt and 3 teaspoons of the pepper. Heat the olive oil in a large cast-iron skillet over medium-high heat. Add the steaks and cook to the desired doneness, 5 to 6 minutes per side for medium-rare. Let rest for 10 minutes. In a small bowl, whisk together the vinegar, extra-virgin olive oil, and the remaining salt and pepper. In a large bowl, combine the radishes, cucumber, and lettuce with the vinaigrette. Slice the steak and serve with the salad.